[zorp] Any plans for SIP support

[Igor S. Livshits]

At 10:24 AM +0100 on 3/14/01, Balazs Scheidler wrote:
>What is SIP good for, and how do you think it could be
>implemented on a firewall?


SIP is a signaling protocol for media streams (e.g., voice over RTP). 
An ideal implementation would include the following ingredients:

1. Open incoming port 5060 (standard SIP port)

2. Dynamic opening and closing of channels for media streams 
(RTP/RTCP) as negotiated by SIP messages

3. NAT for both SIP and media

4. Rewriting of SIP payloads to correspond to NAT (i.e., a 
special-purpose slim SIP proxy)

For some examples, take a look at the Cisco PIX "sip fixup" [payload 
adjustment lacking], Aravox media firewall coupled with a dynamicsoft 
firewall control proxy, the offering from Microappliances 
<http://www.microappliances.com/applications/ALG/alg.html> [limited 
information on functionality], and the Linux SIP masquerade module 
<http://www.siphappens.com/masquerade/draft-biggs-sip-nat-00.txt>.

Thanks, Igor